#include <bits/stdc++.h>
using namespace std;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N; cin >> N;
    vector<int> renchon(N,1);
    for (int i=0;i<N;++i){
        for (int j=0;j<N;++j){
            string greeting; cin >> greeting;
            if (i==j) continue;
            if (greeting!="nyanpass") renchon[j]=0;
        }
    }
    int ans=-1;
    for (int i=0;i<N;++i){
        if (renchon[i]){
            if (ans!=-1){
                cout << -1 << '\n';
                return 0;
            }
            ans=i+1;
        }
    }
    cout << ans << '\n';
}